Tuesday, October 18, 2011

News: Why Not Space?

This author looks at some of the negative aspects of space travel and colonization. I think it is worth being a realist and considering both the benefits and problems in any proposition. This author has some cogent arguments. He could be right, he could be wrong but we should consider his ideas, I think.

"But I want to caution against harboring illusions of space as the answer to our collision course of growth on a finite planet. We live at a special time. We have enjoyed spending our inheritance of fossil fuels, and are feeling rather heady about our technological prowess. For many generations now, we have ridden an exponential growth track, conditioning ourselves to believe that our upward trajectory is an eternal constant of our existence."

4 comments:

This is a stupid argument! There is no sense in discussing any plans in this direction at all. We know way to little about it there is no infrastructure even close to providing an environment where it is logical to consider this even a reality. Until we can build spacecraft in space it's moot. We need to concentrate on getting commercial space off the ground and in orbit first. I'm not talking about Space-X that is snuggled up so close to NASA it might as well be the same thing! We need companies that can provide access to space before we even talk about putting people up there! We need an infrastructure on a scale unseen or imagined by many to even consider this a possibility. We have no such infrastructure and I don't see anyone really working on it! It's not at all just about ROCKETS it's about the infrastructure that is needed first! Cart before horse indeed! We need to think about the infrastructure required and build that first! Until then you might as well just burn your money in the fireplace.

Murphy's math may be wrong, but he does bring up some interesting points.

Even if we disagree with someone like that, I think it is worth at least considering what they say. We should not be so blinded by our dreams that we fail to see reality.

We must temper our dreaming with good doses of reality. The one reality is that space is expensive and we have to seek to lower the costs before we realize our visions of space expansion. Remember, no bucks, no Buck Rogers....

Murphy correctly focuses on Tsiolkovsky's rocket equation as a major challenge in achieving economical space flight.

Extra terrestrial propellant sources close in terms of delta V (change in velocity) Could do a lot in enabling lower mass fractions and reusable space craft. What propellant sources does he look at? Titan and Jupiter!

There are two possible sources of extra terrestrial propellant much closer. The cold traps at the lunar poles and Near Earth Asteroids (NEAs).

In another blog article, Stranded Resources, Murphy attempts to show retrieving asteroids isn't practial. He stipulates 5 kilometers per second to retrieve an asteroid and methane/oxygen as propellant which has an exhaust velocity of about 3 kilometers per second. Compare Murphy's scenario with the Keck asteroid retrieval proposal. They point at NEAs that can be parked in lunar orbit with .2 km/s (not 5 km/s). They propose using xenon in Hall thrusters whith an exhaust velocity of about 30 km/s.

Using Murphy's scenario, propellant mass needed to retrieve an asteroid would be more than the asteroid's mass. In the Keck proposal, propellant mass is about 1/100 of the asteroid mass.

Maybe space is too expensive. But we spend more on cosmetics than space. Half of a percent of our budget is NASA. I would argue space is a good investment worthy of more funding.

Murphy tries show it's an investment doomed to failure. But his numbers are simply wrong. If he were a freshman aerospace student, his mangled delta V figures would be merely embarrassing. From a physics professor, they're inexcusable. He is not credible.